Decorative material and decorative plate

ABSTRACT

A translucent decorative board for use, e.g., as a window pane, light shade, partition or door pane is disclosed. The decorative board is comprised of a translucent substrate board and translucent cover sheets bonded to the surfaces of the substrate board. The substrate board is generally thermoplastic and the decorative cover sheets are thermosetting. The thermosetting sheet may comprise a substrate paper sheet and a thermosetting resin impregnated in the sheet.

FIELD OF THE INVENTION

[0001] This invention relates to a translucent decorative board or panefor use, e.g., as a translucent or semitransparent partition panel,table top, door panel, window pane or illuminator screen, e.g., in arestaurant, hotel, department store, hospital, office or house.

BACKGROUND ART

[0002] Decorative boards or panels are conventionally used as interiorbaseboards, wainscots, decoration panels, etc. Conventionally there is adecorative board comprising a plastic (such as acrylic or polyvinylchloride) substrate and a patterned paper or sheet, which arethermo-compression bonded together. Such conventional boards providecertain optical transmittance and are widely used, e.g., as flooring,ceiling, wall or light shielding materials. There is also a glass boardfor use, e.g., as a table top or shelf board, comprising a plastic filmand a solid or thick (often as thick as 5 mm or over) glass board, whichare bonded together.

[0003] A relatively fragile conventional decorative board is liable tocracking or flaws and therefore generally unfit for use as a shelf boardor table top which requires considerable resistance against physicalshocks and/or pressing force. A relatively solid and sturdy conventionalglass board comprising a glass board and a plastic film is relativelyhard to process such as cutting and often excessively heavy to handle.

[0004] Accordingly, it is a “first” object of the present invention toprovide a decorative board which is translucent or semitransparent,lighter than glass, easy to process, resistant to cracking and flawing,and excellent in overall mechanical properties.

[0005] A single-color board is disclosed in JP Patent Publication No.5-39187, which comprises a substrate board containing a polymericpigment, which is sandwiched by identically colored sheets. Thisdecorative board material is not sufficiently translucent and thus isnot particularly suitable for use against a light source.

[0006] The inventors of the present invention originally aimed atproviding a translucent or semi transparent decorative board by directlycoloring a polymeric substrate. However, such a translucent decorativeboard posed a number of problems. Some of the major problems are; a)difficulty in controlling colors; b) relatively limited colors as aresult of manufacturing restrictions; c) requirement of a largemanufacturing plant; d) relatively low productivity; e) unfitness forsmall quantity production; and f) relatively poor mechanical properties.

[0007] Accordingly, it is a “second” object of the present invention toprovide an “evenly-colored” decorative board which can be economicallyproduced even in a small quantity, where its transparent substrate andcolored cover layers together provide an “illusion” of an evenly coloredboard.

[0008] There also conventionally exists a translucent (semitransparent)decorative board for use as a window pane, door board or illuminationshade, comprising a transparent substrate such as a glass board and acolored or patterned fabric or plastic sheet bonded to the transparentsubstrate. Such a conventional decorative board is short of providing“special” effects or satisfactory transparency.

[0009] Accordingly, it is a “third” object of the present invention toprovide a decorative board or pane which provides “fancy” transparencyor translucency as well as soothing effects on viewers' mental states.

[0010] Other objects of the present invention will become apparent fromthe following descriptions.

SUMMARY OF THE INVENTION

[0011] The present invention is summarized hereunder using the drawingswhich accompany the specification, which will facilitate easyunderstanding of the present invention by the readers.

[0012] A translucent decorative board of the present invention comprisesa translucent thermoplastic board and a translucent thermosetting sheetor sheets bonded to a surface or surfaces of the thermoplastic substrateboard.

[0013]FIG. 1 shows a decorative board 10 according to an embodiment ofthe present invention comprising a translucent thermoplastic substrateboard 12 (which is considerably lighter and easier to process than aglass board), and translucent thermosetting sheets 11,13, whose surfacesare harder than the surfaces of the thermoplastic board 12. Thethermosetting sheets 11,13 sandwich the thermoplastic board 12 as shownin FIG. 1. A suitable translucent polymeric material for thethermoplastic board 12 may be an acrylic resin, polyvinyl chlorideresin, polycarbonate resin, polyethylene phthalate resin or olefinresin. Preferably, the thickness of the thermoplastic substrate board 12is 1 mm to 30 mm.

[0014] The modifiers “transparent” and “translucent” as used herein aresometimes interchangeable. The terms “translucency” and “transparency”as used in this specification are meant to provide an opticaltransmittance of “10% or greater” (JIS K7105: Japanese IndustrialStandard). An optical transmittance of “10% to 50%” is particularlypreferred for the “translucency” of the present invention.

[0015] Polymeric or resin materials for the thermosetting sheets 11,13may be selected from the polymer or resin group consisting of melamineresin, diallylphthalate resin, unsaturated polyester resin andpolyurethane resin. These resin materials generally providetranslucency, light resistance, surface hardness and resistance toflaws.

[0016] It is preferred that the thermosetting sheets 11,13 each comprisea fibrous substrate or paper substrate where a thermosetting polymericmaterial is impregnated, which is chemically resistant and stainresistant. It is preferred that the fibrous or paper substrate is atranslucent sheet or paper containing less than 1% ash or a concealedpaper which may contain more than 1% ash. Generally, it is preferredthat the ash content of the substrate board is below 5%. If the ashcontent is over 5%, the optical transmittance of the decorative board ofthe present invention will become “poor” or less than the desired 10%.

[0017] The thermosetting sheets 11,13 may each comprise a woven ornonwoven fibrous substrate sheet of inorganic or organic fibers, inwhich a thermosetting resin is impregnated. This construction providesan excellent tensile strength and resistance against stretching orshrinkage, which assists in providing the decorative board product ofthe present invention with excellent tensile strength, modulus ofelasticity, dimensional stability and impact resistance.

[0018] The decorative board incorporating such thermosetting sheets canbe subjected to drilling and/or punching processes without cracking orchipping, capable of accepting use of a screw or bolts without damagesthereto.

[0019] The inorganic fibers may be selected from the fiber groupconsisting of glass fibers, carbon fibers and ceramic fibers. Theyprovide the thermosetting sheets 11,13 with excellent tensile strengthand resistance against stretching, providing the decorative board of thepresent invention with excellent modulus of elasticity and resistanceagainst bending.

[0020] The organic fibers may be selected from the fiber groupconsisting of polyester fibers, nylon fibers, rayon fibers, acrylicfibers, vinylon fibers, polyethylene fibers, polypropylene fibers,cotton fibers, silk fibers, wool fibers, bast fibers, and pulp fibers.They provide the thermosetting sheets with excellent physical toughness,providing the decorative board of the present invention with excellentimpact resistance.

[0021] Japanese Patent Laid-Open Publication No. 11-291423 teaches adecorative board comprising a polyolefin plate containing inorganicparticles and a protection sheet bonded to the polyolefin plate. Thisdecorative board does not provide satisfactory strength nor workability,totally lacking in optical transmittance.

[0022] The thermoplastic board 12 and the thermosetting sheets 11,13 canbe bonded together, e.g. through the following processes to provide adecorative board 10 of the present invention.

[0023] One bonding method comprises forming thermosetting sheets 11,13by thermo-compression forming means, and respectively bonding thethermosetting sheets 11,13 onto both surfaces of a thermoplastic board12 with an adhesive. The adhesive should be transparent and lightresistant. A polyurethane adhesive can be advantageously used. In orderto provide good adhesion, the thermoplastic board 12 may be surfacetreated to provide good wettability, e.g., by corona discharge means orplasma discharge means.

[0024] Another bonding method comprises preparing prepregs or compositepolymeric layers by impregnating an appropriate thermosetting resin intoa plurality of substrates prepared of inorganic or organic fabrics(woven or nonwoven fabrics) or paper, and thermo-compress the layeredprepregs-on both surfaces of the thermoplastic board 12, preferablyusing hot-cold press means. The hardening temperature of thethermosetting resin must be equal to or below the softening temperatureof the thermoplastic board 12. The adjustment of the hardeningtemperature of the preregs may be made by selective use of hardeningagents.

[0025] In order to achieve the “second” object of the present inventionwhich is set forth earlier, a translucent substrate board is sandwichedby translucent decorative surface sheets so as to look “colored” or“patterned” similarly or identically with the surface sheets. In otherwords, the decorative board produces an illusion that the transparentsubstrate board is also “similarly colored.”

[0026] The wording “similarly colored” as used herein is in accordancewith the color dictionary entitled “Dictionary of Colors” published byJapan Color Research Center/Japan Color Research Company (1stedition/Sep. 15, 1973), which divides colors into sixteen(16) basicsimilarity blocks.

[0027] The “second” object of the present invention is achieved byprovision of a decorative board 20 as shown in FIG. 7, which comprises atranslucent substrate board 22 whose both surfaces are covered withtranslucent decorative sheets 21,23. The decorative sheets 21 and 23preferably possess an identical color or similar color. The light or raycoming at an angle onto and into the decorative board 20 partiallyreflects on the outer surface of the decorative sheet 21 and on theinner surface of the other decorative sheet 23 as schematically shown inFIG. 7, “carrying out” the color where they reflect, providing a phantomimpression or look that the translucent substrate board 22 is alsocolored identically or similarly.

[0028] The decorative sheets 21,23 may be alternatively or additionallyprovided with an identical colored pattern, in which case, thetranslucent substrate board 22 provides a phantom impression that thesubstrate board 22 is patterned identically with the decorative sheets21,23.

[0029] The translucent substrate board 22 may be prepared of acrylicresin, polyvinyl chloride resin, polycarbonate resin, polyethyleneterephthalate resin or olefin resin. In an embodiment, the higher theoptical transmittance, the better for the substrate board 22.Preferably, the optical transmittance of the substrate board is greaterthan 10%. It is preferred that the thickness of the substrate board 22is 1 mm to 20 m. The substrate board 22 maybe a glass board pane.

[0030] The decorative sheet 21,23 may be provided as a paint layer,print layer, colored film, decorative paper or colored facing layerwhich possesses a degree of translucency (optical transmittance of 10%or greater). It is advantageous that the decorative sheets 21,23 are apolymer impregnated sheet since a resin impregnate sheet providesexcellent impact resistance, flaw resistance and bend resistance.

[0031] The resin material which may be advantageously impregnated in thesubstrate sheet material for the decorative sheets 21,23 may be selectedfrom the translucent thermosetting resin group consisting of melamineresin, epoxy resin, phenol resin, diallylphthalate resin and unsaturatedpolyester resin.

[0032] The substrate sheet material of the decorative sheets 21,23 maybe an organic or inorganic fabric sheet or paper. The organic fibers maybe polypropylene fibers, polyester fibers or alamido fibers. Theinorganic fibers may be glass fibers, alumina fibers or silica fibers.The substrate sheet material may be printed with an attractive patternin color or colors. The decorative sheets 22,23 may each be covered witha hard type plastic cover layer for protection of the surfaces of thedecorative sheets 21,23.

[0033] The “third” object of the present invention is achieved by thefollowing structural constitution which provides an integratedtranslucent decorative board, comprising a translucent glass or plasticpane and a translucent decorative panel, which are secured to eachother. Such a decorative board may be advantageously used as a windowpane and produces a visionary interior atmosphere.

[0034] The translucent decorative panel for the glass-type decorativeboard of the present invention may be provided through the steps offorming a plurality of partially overlapping print layers on atranslucent paper sheet, and impregnating a thermosetting resin in thepaper sheet together with the print layers provided thereon. Theplurality of partially overlapping print layers may be advantageouslyprovided by printing micro-sized color dots.

[0035] As set forth, the translucent paper sheet having partiallyoverlapping print color dots is impregnated with a translucent type ofthermosetting resin to provide a translucent decorative panel whichrenders the color dots underneath the translucent resin to be seenthrough.

[0036] Such partially superimposed color dots may be advantageouslyprovided by silk screening means. Silk screening processes are repeatedas many times as desired to provide partially superimposed dots ofdifferent colors on the translucent substrate paper. The partiallysuperimposed dots of different colors will provide an attractive andfancy color appearance. The decorative board of the present inventionintegrating such a decorative panel on a translucent glass or glass-likeboard can provide a unique and visionary appearance when light from alight source such as the sun pours through the translucent decorativeboard.

[0037] A Japan paper sheet or “washi” which itself provides a unique andtasteful pleasure and is excellent in mechanical properties may beimpregnated with a translucent thermosetting resin and additionally usedbetween two translucent resin impregnated paper sheets. The Japan papersheet when impregnated with a translucent type resin will itself becometranslucent. Japan paper can be easily and directly colored or providedwith a colored design pattern during its traditional uniquemanufacturing processes, which provides the decorative board of thepresent invention with an additional special taste that other materialscannot and will eliminate subsequent printing processes.

[0038] The glass-type decorative board of the present invention mayalternatively comprise a glass pane and a translucent decorative panelprovided separately, the decorative panel being secured to the glasspane with suction cups as shown in FIGS. 20 and 21.

[0039] Another glass-type of a decorative board may comprise adecorative sheet which is patterned with printed patches or spots andimpregnated with a thermosetting resin. The printed patches provideshade images while other portions (non-printed portions) providerelatively bright images, creating a tasty and fancy contrasting image.

[0040] When the decorative board is used as a window pane of a houseroom or hotel lounge, the house room or hotel lounge will be providedwith a unique visionary atmosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041]FIG. 1 is a perspective view of a decorative board according toEmbodiment 1(1) of the present invention;

[0042]FIG. 2 is a sectional view of the decorative board of FIG. 1;

[0043]FIG. 3 is a sectional view of a decorative board according toEmbodiment 1(2) of the present invention;

[0044]FIG. 4 is a sectional view of a decorative board according toEmbodiment 1(3) of the present invention;

[0045]FIG. 5 is a perspective view of a decorative board according toEmbodiment 1(4) of the present invention;

[0046]FIG. 6 is a sectional view of the decorative board of FIG. 5;

[0047]FIG. 7 is a sectional view of a decorative board according toEmbodiment 2(1) of the present invention;

[0048]FIG. 8 is another sectional view of the decorative board of FIG.7;

[0049]FIG. 9 is a perspective view showing a use of a decorative boardaccording to Embodiment 3(1) of the present invention;

[0050]FIG. 10 is a sectional view of the decorative board of FIG. 9;

[0051]FIG. 11(a) is a micrographical sectional representation whichschematically shows superimposed print dots on a translucent substratesheet according to Embodiment 3(1) of the present invention;

[0052]FIG. 11(b) is a sectional representation which shows anotherdecorative sheet according to Embodiment 3(1) of the present invention;

[0053]FIG. 12 is a perspective view showing a use of a decorative boardaccording to Embodiment 3(2) of the present invention;

[0054]FIG. 13 is a sectional view of a decorative board according toEmbodiment 3(2) of the present invention;

[0055]FIG. 14(a) is a perspective view showing a manufacturing processof a decorative board according to Embodiment 3(2) of the presentinvention;

[0056]FIG. 14(b) is a perspective view showing the completed state ofthe decorative board of FIG. 14(a);

[0057]FIG. 15(a) is a perspective view showing a manufacturing step ofanother decorative board according to Embodiment 3(2) of the presentinvention;

[0058]FIG. 15(b) is a perspective view showing the completed state ofthe decorative board of FIG. 15(a);

[0059]FIG. 16 is a perspective view showing a use of a decorative boardaccording to Embodiment 3(3) of the present invention;

[0060]FIG. 17 is a sectional view of a decorative board according toEmbodiment 3(3) of the present invention;

[0061]FIG. 18(a) is a sectional view of a decorative board according toEmbodiment 3(3) of the present invention;

[0062]FIG. 18(b) is a plan view of the decorative board of FIG. 18(a);

[0063]FIG. 19(a) is a micrographic representation which schematicallyshows a gravure printing step for a decorative board according toEmbodiment 3(3) of the present invention;

[0064]FIG. 19(b) schematically shows a manufacturing process of thedecorative board of FIG. 19(a);

[0065]FIG. 20 is a perspective view showing another type of decorativeboard of the present invention;

[0066]FIG. 21 is a sectional view of the decorative board of FIG. 20.

DEFINITION OF THE NUMERALS USED

[0067]11 . . . thermosetting resin decorative sheet

[0068]12 . . . thermoplastic resin substrate board

[0069]13 . . . thermosetting resin decorative sheet

[0070]10 . . . decorative board

[0071]21 . . . decorative sheet

[0072]23 . . . decorative sheet

[0073]22 . . . substrate board

[0074]20 . . . decorative board

[0075]1 . . . superimposed print layers

[0076]2 . . . translucent paper sheet

[0077]6 . . . paper sheet

[0078]3 . . . synthetic resin

[0079]7 . . . synthetic resin

[0080]4 . . . resin impregnated paper sheet

[0081]5 . . . Japan paper or vashi

[0082]31A . . . decorative sheet

[0083]31B . . . decorative sheet

[0084]31C . . . decorative sheet

[0085]311 . . . print layer

[0086]312 . . . print layer

[0087]313 . . . print layer

[0088]314 . . . printed portion

[0089]315 . . . non-printed portion

[0090]316 . . . pattern

[0091]9 . . . original form

[0092]90 . . . convex-concave portion

[0093]91 . . . concave portion

[0094]92 . . . convex portion

[0095]95 . . . flat portion

[0096]100 . . . decorative board

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0097] The present invention is described in more detail in accordancewith various embodiments of the present invention using the drawingsthat accompany the specification. These embodiments are to be construedas illustrating the present invention only, and not as limiting thescope of the present invention.

[0098] First of all, several embodiments which attain the “first” objectof the present invention are described using FIGS. 1-4.

Embodiment 1(1)

[0099] A polypropylene resin (olefin resin) was used to provide athermoplastic substrate board 12. Each surface of the substrate board 12was provided with a diallylphthalate decorative sheet 11,13 as athermosetting resin sheet, which was to be bonded to the substrate board12 with an adhesive as follows so as to provide a decorative board 10shown in FIG. 2.

[0100] The substrate board 12 (a product of Mitsui Kagaku Plastics), 2.0mm thick, was treated by corona discharge means to provide goodwettability (50 dyn). A translucent paper sheet (60 g/m2) which hardlycontained ash was impregnated with a diallylphthalate resin (hardeningcatalyst: BPO: a product of Kawaguchi Yakuhin K.K.) to a rate 100 g/m2,which was thermo-compressed in a double-belt press to a 0.15 mm thicksheet. Two of such sheets 11,13 were prepared.

[0101] A polyurethane adhesive (G-5081) was applied on a surface of eachof the diallylphthalate sheets 11,13. After the adhesive dried, thesheets 11,13 were respectively placed on the surfaces of the substrateboard 12. The sheets 11,13 were then thermo-compressed together with thepolypropylene board 12 in a heat roll at about 60° C. The sheets and theboard were bonded securely together, and a decorative board 10 of thepresent invention was completed after two-day aging at about 40° C.

Embodiment 1 (2)

[0102] A G-PET (product name) resin board (modified polyethylenephthalate resin board: Takiron), 2.0 mm thick, was used as athermoplastic resin substrate board 12. Each side of the board wasprovided with a prepreg (sheets) 11,13, which was bonded to thesubstrate board 12 by thermo-compression. The prepreg sheet comprised aglass fiber nonwoven fabric sheet (60 g/m2) impregnated with adiallylphthalate resin (200 g/m2). The prepregs 11,13 were bonded to theG-PET substrate board 12 by thermo-compressing (hot-cold press at 10kg/cm2 under up to 100° C.), and a decorative board 10 was prepared.

Embodiment 1(3)

[0103] An acrylic substrate board (2.0 mm thick) was used as athermoplastic substrate board 12, and a diallylphthalate resin was usedas a thermosetting resin. The substrate board 12 was surface treated bycorona discharge means to provide wettability 50 dyn. A translucentpaper sheet (60 g/m2) containing no ash was impregnated with thediallylphthalate resin (BPO hardening catalyst) to a rate 100 g/m2,which was bonded to a surface of the substrate board 12 bythermo-compression at about 150° C., 18 kg/cm2 to produce a decorativeboard 10 having a single decorative sheet 11 (see FIG. 4).

[0104] Properties of the decorative boards 10 prepared according toEmbodiments 1(1)-1(3) were studied. For comparison, conventionaldecorative boards were also prepared as Comparisons 1(1), 1(2) and 1(3)Table 1 shows the result of the comparison. TABLE 1 Emb. Emb. Emb. Com.Com. Com. 1-1 1-2 1-3 1-1 1-2 1-3 Top paper + glass paper + poly- G-PETacrylic DAP non- DAP propyl- material woven + ene DAP Int. poly- G-PETacrylic poly- G-PET acrylic propylene material propyl- material eneBottom paper + glass (none) poly- G-PET acrylic DAP non- propyl-material woven + ene DAP Thick- 2.5 mm 2.2 mm 2.25 2.0 mm 2.0 mm 1.5 mmness mm Hardness 70 g 70 g 70 g <10 g <10 g 10 g (surface) Flexural 72Mpa 170 Mpa 150 43 Mpa 77 Mpa 70 Mpa Strength Mpa Flexural 3.3 Gpa 7.3Gpa 3.0 Gpa 1.4 Gpa 2.2 Gpa 2.0 Gpa Modulus Impact 1100 mm 1200 mm 10001200 500 mm 500 mm Resistance mm mm Workabil- circle circle circlecircle circle circle ity saw saw saw saw saw saw usable usable usableusable usable un- usable Boring no no no cracks cracks cracks Perfor-cracks cracks cracks mance

[0105] Comparison 1(1) used a 2.0 mm thick polypropylene board,Comparison 1(2) used a 2.0 mm thick G-PET board, and Comparison 1(3)used a 1-5am thick acrylic board.

[0106] The surface hardness, flexural strength, flexural modulus, andimpact resistance in Table 1 were measured according to the JIS K6902standard. The boring performances were tested using a 5 mm-diameterdrill.

[0107] Embodiments 1(1), 1(2) and 1(3) provided very good surfacehardness, flexural strength, flexural modulus and impact resistance,while Comparison 1(1) provided poor surface hardness, flexural strengthand flexural modulus and Comparison 1(2) provided poor surface hardness,flexural strength, flexural modulus and impact resistance. Further, whenEmbodiments 1(1), 1(2) and 1(3) were wiped with acetone, no degradationof the surfaces was observed, while the wiping with acetone ofComparisons 1(1), 1(2) and 1(3) whitened the surfaces. The opticaltransmittances of Embodiments 1(1), 1(2) and 1(3) were respectively 20%,25% and 30%. Embodiments 1(1), 1(2) and 1(3) were only about ⅓ of glassin weight (<0.8 specific gravity), while Comparison 1(3) had a specificgravity of 1.5.

[0108] As described, the surface hardness, flexural strength andflexural modulus can be excellently improved by providing athermosetting sheet or sheets on the surfaces of a thermoplastic board.Impact resistance can also be greatly improved by adequately selectingthe thermosetting resin materials. The thermoplastic resin boards weretranslucent (optical transmittance 10% or better), which provided fancyappearance to the finished decorative boards. It is to be noted that thetranslucent substrate boards 12 of those embodiment decorative boards 10of the present invention appeared “colored” the same with the color orcolors of the covering decorative sheets 11,13 as can be appreciatedeasily by artisans of the relevant fields.

[0109] The decorative board of Embodiment 1(3) had a thermosetting sheetonly on one surface thereof, which warped 3 mm for every 1 m after leftat 80° C. for an hour, while the decorative boards of Embodiments 1(1)and 1(2) having two cover sheets each did not warp practically at alland were stable, which is evidence that two thermosetting sheets aremore preferable to only one sheet. However, such small warping ispractically ignorable.

[0110] The following other embodiment decorative boards, Embodiments1(4) and 1(5), were prepared so as to achieve the “first” object of thepresent invention, which are partially shown in FIGS. 5 and 6.

Embodiment 1(4)

[0111] A decorative board 10 of this embodiment comprised athermoplastic polypropylene board 12 a (olefin board) and thermosettingdiallylphthalate sheets 11 a,13 a which were bonded to the surfaces ofthe polypropylene board 12 a.

[0112] The decorative board 10 of this embodiment was prepared asfollows. A 1.0 mm thick translucent polypropylene board 12 a was surfacetreated by corona discharge means to provide the surfaces thereof withwettability 50 dyn. A translucent paper sheet (60 g/m2) wasthermo-compression bonded (150° C., 20 kg/cm2) with a diallylphthalateresin impregnated sheet to provide a 0.15 mm thick decorative sheet. Twosuch diallylphthalate resin sheets 11 a and 13 a were prepared. Apolyurethane adhesive (G-5081) was applied on the decorative sheets 11a,13 a. The decorative sheets were then placed respectively on thesurfaces of the polypropylene board 12 a. The decorative sheets 11 a,13a and the substrate board 12 a were bonded together bythermo-compression to provide a decorative board 10 as shown in FIGS. 5and 6.

Embodiment 1(5)

[0113] (1) A formaldehyde aqueous solution (37%) was blended with amelamine resin (1.7 mol/1 mol). The pH of the solution was adjusted topH 9.0 with sodium hydroxide. The blend was then heated to about 90° C.and held for 60 min. to provide a thermoplastic melamine resin.

[0114] (2) A substrate sheet impregnated with the thermoplastic melamineresin was placed on a surface of a polyethylene board, which werethermo-compressed at 140° C., 7.85 Mpa to provide a decorative board.

[0115] Mechanical properties of the decorative boards of Embodiments1(4) and 1(5) were studied. For comparison, Comparisons 1(4) and 1(5)were also prepared (provided below). Table 2 shows the comparisonresult. Embodiments 1(4) and 1(5) respectively had opticaltransmittances of 20% and 25%. TABLE 2 Rate of Dimensional Impact FlexCutting Change Resistance Radius Performance Emb. +0.1% 1000 mm 50 mmeasy to saw 1 (4) with circle saw Emb. +0.1% 1200 mm 60 mm easy to saw 1(5) with circle saw Com. +0.8%  300 mm not can be sawn with 1 (4)possible circle saw Com. +0.3%  300 mm not hard to saw 1 (5) possiblewith circle saw

Comparison 1(4)

[0116] Nine sheets of paper where diallylphthalate resin was applied oneach translucent sheet (60 g/m2) were thermo-compressed and bondedtogether at 150° C., 20 kg/cm2 to provide a 1.3 mm thick decorativeboard.

Comparison 1(5)

[0117] The decorative board of this comparison was a 1.5 mm thickacrylic board.

[0118] An additional conventional comparison board, Comparison 1(6), wasalso prepared, and it was found that the decorative board of Embodiment1(6) did not provide physical properties that were comparable to thoseof the Embodiments 1(4) and 1(5).

Comparison 1(6)

[0119] As taught in JP Patent Laid-Open Publication No. 11-291423, apolyolefin sheet consisting of polyethylene (100 parts by weight),styrene-butadiene rubber (60 parts by weight) and calcium carbonate (25parts by weigh) was surface treated with an urethane resin and hardenedto provide a decorative board.

[0120] Two embodiment decorative boards, Embodiments 1(7) and 1(8), wereadditionally prepared to deepen the study of the advantageous featuresof the present invention.

Embodiment 1(6)

[0121] The translucent paper for the decorative cover sheet ofEmbodiment 1(4) was replaced by white pattern paper (kw-01u; KojinCompany, 7% ash content) and a decorative board was prepared.

Embodiment 1(7)

[0122] The translucent paper for the decorative cover sheet ofEmbodiment 1(4) was replaced by conceal paper (PK-130; Kojin Company, 2%ash content).

[0123] The decorative boards of Embodiments 1(6) and 1(7) had surfacehardness, flexural strength, flexural modulus, impact resistance,workability and boring performance which were comparable to Embodiment1(4). However, the optical transmittances of Embodiments 1(6) and 1(7)were respectively only 5% and 15%.

[0124] The “rate of dimensional change” as used in Table 2 was the rateof extension or difference in dimension between the measurements of thesubject boards taken after the subject boards were held at 20° C., 40%RH (relative humidity) for 24 hs. and the subject boards were held at20° C., 95% RH (relative humidity) for 24 hs. The “impact resistance”was the measurements of the maximum heights where a steel ball, 28 g,was dropped onto the subject boards without resulting in breaking orcracking of the boards. The “flex radius” was the maximum radiuses ofthe subject boards when forcedly wound around a cylinder (50 mm radius)without cracking. The “cutting performance” was the workability using acircle saw.

[0125] Table 2 clearly shows superiority of Embodiments 1(4) and 1(5)over Comparisons 1(4) and 1(5) practically in every aspect of the testedfeatures. The optical transmittances of Comparison 1(6) was mere 1%. Theimpact resistance of Comparison 1(6) was “100 mm” and it was virtuallyimpossible to bend the board of Comparison 1(6) without cracking theboard Workability with a circle saw of Comparison 1(6) was poor.

[0126] Some of the excellent physical and appearance properties of thedecorative boards according to Embodiments 1(1) to 1(7) are summarizedhereunder.

[0127] (1) They provide excellent optical transmittance, as melaminelayers, diallylphthalate layers or urea layers are formed on olefinboards;

[0128] (2) They provide excellent flexibility, excellent resistanceagainst cracking and flawing, and excellent workability; and

[0129] (3) They provide excellent size stability under humidatmospheres, as thermosetting layers are provided on olefin boards.

[0130] The olefin boards used in Embodiments 1(4) and 1(5) may bereplaced by olefin foam boards, which are lighter and thus easier totransport and handle.

[0131] Other decorative boards were prepared in order to achieve the“second” object of the present invention, part of which are shown inFIGS. 7 and 8.

Embodiment 2(1)

[0132] Each surface of a translucent or transparent acrylic board(Mitsui Kagaku) 22 was provided with a colored translucent vinylchloride sheet (IKC) 21,23 having an adhesive layer, which was bonded tothe surface with roll press means, and a decorative board 20 wasproduced. The sunlight coming onto the decorative board 20 partiallyreflected on the surface and partially advanced into the decorativeboard 20, coming out of the decorative board 20 from the transparentboard side 22 a as shown in FIG. 7, providing an illusion that thetranslucent or transparent substrate board 22 was tinted the same coloras the decorative colored sheets 21,23.

[0133] When a side edge of the decorative board 20 was cut or processedround as shown in FIG. 8, the round side edge 22 a provided the illusionmore visibly, which was an improvement over a decorative board withoutsuch a round cut edge.

Embodiment 2(2)

[0134] Colored cellophane films 21,23 were bonded on the surfaces of a 5mm thick glass pane 22. This decorative board 20 provided the sameillusionary effects as the decorative board of Embodiment 2(1).

Embodiment 2 (3)

[0135] Yellow fabric substrate sheets were impregnated with a melamineresin and dried into B-stage, which were respectively placed on thesurfaces of a 2.0 mm thick acrylic board 22 and bonded to the surfaceswith an urethane adhesive (G-5081) to provide a yellow decorative board.This decorative board provided the same illusionary effects as thedecorative boards according to Embodiments 2(1) and 2(2).

Embodiment 2(4)

[0136] A yellow glass fabric sheet and an orange glass fabric sheet wereimpregnated with a diallylphthalate resin (B.P.O.; Kawaguchi Yakuhin)and dried, which were bonded together by low pressure continuation pressmeans at 10 kg/cm2, 140° C. to provide a laminate decorative sheet. Twoof such laminate sheets were respectively bonded on the surfaces of a2.0 mm thick vinyl chloride board 22 (Takiron) with an urethane adhesive(G-5081) to provide a yellow decorative board 20. This decorative boardprovided the same illusionary effects as Embodiments 2(1), 2(2) and2(3).

Embodiment 2(5)

[0137] Two yellowish translucent paper sheets (60 g/m2) having identicalprinted patterns were impregnated with a diallylphthalate resin(hardening catalyst; B.P.O.; Kawaguchi Yakuhin), which were respectivelybonded by thermo-compression means at 20 kg/cm2, 140° C. on the surfacesof a polypropylene board which had been corona discharge treated. Thisdecorative board provided the same illusionary effects as Embodiments2(1) to 2(4).

[0138] In order to study the advantageous features of Embodiments 2(1)to 2(5) by comparison, Comparisons 2(1),2(2) and 2(3) were also preparedas follows.

Comparison 2(1)

[0139] A decorative board was prepared according to JP PatentPublication No. 5-39187. A green pattern paper sheet (112 g/m2)containing 34.4 wt % titanic acid and bleached craft paper sheets (each184 g/m2) containing 4.4 wt % inorganic green pigment were impregnatedwith a melamine resin up to 55 wt %. The pattern paper sheet and four ofthe craft paper sheets were bonded together at 145° C., 80 kg/cm2 toprovide a decorative board (the pattern paper sheet on the top), whosetop and bottom surfaces had an identical green color.

Comparison 2(2)

[0140] A colored acrylic board obtained commercially (Mitsubishi Rayon;AcryLight) was directly made into a decorative board.

[0141] The optical transmittance, impact resistance, flexural strengthand surface hardness of the decorative boards of Embodiments 2(1) to2(5) and Comparisons 2(1) and 2(2) were respectively measured inidentical manners with the measurement methods set forth. Additionally,the rates of dimensional changes were measured also identically.

[0142] The optical transmittance measurements were taken against visiblelight. The measurements of flexural strength utilizes 3-point flexuraltesting. The surface hardness measurements were taken in accordance withJIS K6902. The measurement results were provided in Tables 3 and 4.TABLE 3 Impact Surface Resist- Flexural Hard- Color Transmittance anceStrength ness T B Sheet Sub. Board mm MPa g Emb. R R 51 88 35 400 100 102-1 Emb. G G 75 90 50 500  90 12 2-2 Emb. Y Y 23 92 12 1200  120 70 2-3Emb. Y O 36 84 20 1200  120 60 2-4 Emb. P P 41 — 14 1200   50 60 2-5Com. G G 400    1.0   0.2 200 110 70 2-1 Com. R R — — 82 300 100 10 2-2

[0143] TABLE 4 Rate of Dimensional Change % Emb. 2-1 0.1 Emb. 2-2 0 Emb.2-3 0.1 Emb. 2-4 0.1 Emb. 2-5 0.1 Com. 2-1 0.6 Com. 2-2 0.1

[0144] Some of the advantageous properties of Embodiments 2(1) to 2(5)are summarized below.

[0145] (1) The transparent substrate boards 22 of those embodimentsprovide an illusion that the transparent boards 22 are “colored” thesame as the decorative sheets 21,23. Such decorative boards 20 can bemanufactured easily and at low costs. They will find their advantageoususe as a door panel, partition, display panels, etc.

[0146] (2) The decorative boards 20 with their side edges cut roundprovide an improvement in the foregoing identical color effect, and willbe able to find additional advantageous uses.

[0147] (3) The decorative boards 20 will provide an illusion that thetransparent substrate boards 22 are also patterned if the decorativesheets 21,23 are patterned, adding still new pleasure.

[0148] (4) The decorative boards 20 incorporating resin impregnateddecorative sheets provide excellent strength, impact resistance andsurface hardness.

[0149] (5) The decorative boards 20 will make excellent displaydecorations taking advantage of their excellent optical transmittance.

[0150] Several other embodiments of decorative boards of the presentinvention are described hereunder which achieve the “third” object ofthe present invention, which should not be construed as limiting thepresent invention.

[0151] A decorative board 30 according to an embodiment of the presentinvention comprises a window glass pane 32 and a translucent decorativepanel 31A bonded to the inner surface of the window pane 32 as shown inFIGS. 9 and 10. In this embodiment, a double coated adhesive tape wasused to bond the glass pane 32 and the decorative panel 31A together.

[0152] As shown in FIG. 11, the decorative panel 31A comprised atranslucent paper sheet 2 hardly containing ash and an integrated printlayer 1. The integrated print layer 1 in this embodiment comprised ayellow layer 311, red layer 312 and black layer 313, which werepartially overlapping one another and were provided on the paper sheet 2by silk screen means. Each layer 311,312,313 comprised numerous printeddots in this embodiment.

[0153] The translucent decorative panel 31A was produced according tothe following processes. The yellow dots, red dots and black dots wereprinted on the translucent paper sheet 2 in this order in thisembodiment by silk screening to provide the integrated printed layer 1,which was impregnated with a thermosetting diallylphthalate resin (DAP)to 60 wt % to provide resin layers 3 (see FIG. 11(b)). The resinimpregnated sheet 2 was then press dried at 160° C., 20 kg/cm2 toproduce a translucent decorative panel 31A.

[0154] The optical transmittances of the decorative panel 31A weremeasured for a) the yellow dot layer, b) the yellow and red dot layerstogether, and c) the yellow, red and black dot layers together inaccordance with JIS K-7361. The measurements provided 30% for the yellowdot layer, 20% for the yellow and red dot layers, and 5% for the yellow,red and black layers. The decorative panel 31A when applied on a windowpane 32 provided a unique and charming contrasting optical appearance.

[0155] In other embodiments, the colors of the dot layers 311,312,313can be differently arranged using the different colors in accordancewith personal tastes. The density of the dots cano be adjusted accordingto personal tastes.

[0156] It is preferred that the ash content in the translucent papersheet 2 is 10 wt % or lower to provide good transparency. It is morepreferred that the ash content is lower than 1 wt %. It is mostpreferred that the ash content is lower than 0.5 wt %. Japan paper orwashi or overlay paper may be advantageously used as the translucentpaper sheet 2 as they provide translucency when impregnated with atranslucent resin.

[0157] The grammage of the translucent paper sheet 2 is preferred to be5-200 g/m2. If less than that, printing on the paper sheet will becomedifficult. If more than that, translucency will be sacrificed. Aplurality of paper sheets 2 may be used in layers to provide atranslucent paper sheet 2 of the embodiments. It is preferred that nomore than eight paper sheets be used so as to hold the boardmanufacturing costs low enough and/or not to sacrifice transparency.

[0158] The impregnating resin for the resin layers 3 is advantageously athermosetting resin such as a diallylphthalate, melamine, epoxy orphenol resin. It is preferred that the resin 3 is impregnated in thedecorative paper sheet 31A between 30 wt % and 80 wt %. Less than 30 wt% will reduce transparency and more than 80 wt % will be uneconomical.

[0159] A cover layer (not shown) such as a resin impregnated paper orpolymeric layer may be applied on the outer (facing towards a room, forinstance) surface of the decorative panel 31A to additionally protectthe surface. The cover layer may include an abrasion resistant particlessuch as silica, alumina or talc particles.

[0160] Use of the decorative board 30 is described in detail using FIGS.12 to 15. A decorative board 30 prepared according to an embodiment foruse as a window pane is shown in FIG. 12 and 13. The decorative board 30comprised a glass pane 32 and a translucent decorative panel 31B whichwas bonded to the inner surface of the glass pane 32 as shown in FIG.13. The decorative panel 31B which was translucent comprised a sheet ofJapan paper 5 sandwiched by resin impregnated sheets 4 as shown in FIG.14(a) and FIG. 14(b).

[0161] Resin impregnated sheets 4 of an embodiment were prepared byimpregnating a melamine resin into sheets of paper (60 g/m2, ashcontents 0.05 wt %) to 60 wt %. A sheet of Japan paper 5, which waspatterned with colored fibers such as a design 33 in FIGS. 15(a) and15(b), was placed between the resin impregnated sheets 4, which werepress heated at 150° C., 80 g/cm2 for 10 min. Alternatively, the design33 may be provided by bark chips. Still alternatively, the Japan papermay selectively include flower petals, wood chips, or colored fibers toprovide unique and attractive designs. When the Japan paper 5 with sucha design is impregnated with a thermosetting resin, the Japan paper 5becomes translucent and the design comes out clearly.

[0162] It is preferred that the ash content of the resin impregnatedpaper sheets 4 is less than 10 wt %. Preferably, the ash content is lessthan 1 wt %, and most preferably it is less than 0.5 wt %. It is alsopossible to provide a pattern to the resin impregnated sheets 4. It ispreferred that the resin content in the sheets 4 is 30 to 80 wt %. It isalso preferred that the paper for the resin impregnated paper sheets 4is 10 g/m2 to 200 g/m2. Less than 10 g/m2 will not provide adequatetransparency when impregnated with a resin, while more than 200 g/m2will lower its flexibility.

[0163] The resin to be impregnated in the resin impregnated paper sheets4 is advantageously a thermosetting resin, such as a diallylphthalate,melamine, epoxy, or phenol resin, which provides a well integrateddecorative panel when thermo-compressed and provides adequate heatresistance.

[0164] The decorative panel 31B advantageously has an opticaltransmittance of 10 to 90%. The Japan paper is advantageously 10-100g/m2. The temperature to perform thermo-compression on the Japan paperand the resin impregnated paper sheets is advantageously 80-200° C. andits pressure is advantageously 10 kg/cm2-100 kg/cm2. A temperature below80° C. may not harden the impregnated resin and a temperature over 200°C. may degrade the impregnated resin. A pressure less than 10 kg/cm2 maynot provide a desired product and a pressure over 100 kg/cm2 may causeescape of the pressurized impregnated resin.

[0165] Another decorative board 30 according to another embodiment ofthe present invention is described hereunder using FIGS. 16-19. Thedecorative board 30 comprised a window glass pane 32 and a decorativepanel 31C which was bonded to the inner surface of the glass pane 32.The decorative panel 31C comprised a translucent paper sheet 6 having adesign 316 consisting of a printed portion 314 and non-print portions315, and resin layers 7 sandwiching the translucent sheet 6 as shown inFIGS. 18(a) and 18(b).

[0166] The translucent paper sheet 6 (60 g/m2, ash content 0 wt %) wasgravure printed the design 316 with a gravure printing machine (PD-6,Fuji Kikai Kogyo) using a negative plate 9 partially shown in FIG. 19(a)which had numerous micro protrusions 90 consisting of convex portions92, concave portions 91 and flat portions 95.

[0167] The negative plate 9 was secured on a roll 40 schematically shownin FIG. 19(b). Ink, blue in this embodiment, was supplied onto the plate9 from an ink supplier 41. The translucent paper sheets 6 were fed on aconveyer 42 placed below the roll 40.

[0168] The printed paper sheet 6 was impregnated with a thermosettingsynthetic resin such as a diallylphthalate resin (DAP) to 60 wt %, whichwas thermo-compressed at 160° C., 20 kg/cm2 to produce a translucentdecorative panel 31C where the design pattern 316 was clearly observed.

[0169] The optical transmittance was measured according to the JISK-7361 standard. The printed portion 314 provided 35% while thenon-print portions 315 provided 55%.

[0170] The printed portion 314 may be provided in dots or as a planeprint layer. It is possible to adjust the optical transmittance of theprinted portion by adjusting the amount of ink or density of the dots orplane print layer.

[0171] It is preferred that the optical transmittance of the printedportion is between 10-50%. It is preferred that the opticaltransmittance of the non-print portions is between 30 to 80%. It is alsopreferred that the difference in optical transmittance between that ofthe printed portion and that of the non-print portions is within therange 5 to 40%.

[0172] The decorative panel 31C may be bonded to another type oftranslucent substrate instead of a glass pane, including an acrylicboard, vinyl chloride board, polycarbonate board, polyethylene phthalateboard and olefin board.

[0173]FIG. 20 shows an embodiment of another type of the decorativeboard of the present invention, where the decorative panel and thesubstrate board are provided separately and detachably. The decorativepanel is secured to the glass pane with suction disk means asillustrated in the figures.

Industrial Utilization of the Invention

[0174] The translucent decorative boards of the present invention can beadvantageously used in a number and variety of ways, providing novelvisionary tastes and soothing feelings to the viewers.

[0175] They can be used as a window pane, partition, decoration board,display board, door panel, etc. The decorative boards of the presentinvention provide excellent physical properties in addition to theirappearance excellency.

[0176] Importantly, the present invention provides such attractivetranslucent decorative boards at very low costs.

What is claimed is:
 1. A decorative board comprising a thermoplasticsubstrate board and at least one thermosetting sheet hardened and bondedto a surface of said substrate board.
 2. A decorative board of claim 1,said thermoplastic substrate board comprising a resin selected from theresin group consisting of acrylic, vinyl chloride, polycarbonate,polyethylene phthalate and olefin resins.
 3. A decorative board of claim1 or 2, said thermosetting sheet comprising a resin selected from theresin group consisting of melemine, diallylphthalate, unsaturatedpolyester and polyurethane resins.
 4. A decorative board of any one ofclaims 1-3, wherein said thermoplastic substrate board is translucent.5. A decorative board of any one of claims 1-4, wherein saidthermosetting sheet comprises a substrate sheet and a thermosettingresin impregnated in said substrate sheet and hardened.
 6. A decorativeboard of claim 5, wherein said substrate sheet is selected from thesheet group consisting of inorganic and organic fiber woven fabrics andnonwoven fabrics, transparent paper sheets containing less than 1 wt %ash, and conceal paper sheets containing more than 1 wt % ash.
 7. Adecorative board of any of claims 1-6, which is translucent.
 8. Adecorative board comprising a translucent substrate board and twotranslucent decorative sheets, wherein said decorative sheets, beingcolored identically with or similarly to each other, are respectivelybonded to the surfaces of said substrate board.
 9. A decorative board ofclaim 8, said decorative sheets respectively having designed featureswhich are essentially identical with each other.
 10. A decorative boardof claim 8, said decorative sheets respectively having designed featureswhich are essentially identical with each other and provided essentiallyat mutually corresponding locations.
 11. A decorative board of any ofclaims 8-10, said substrate board comprising a thermoplastic resin. 12.A decorative board of any of claims 8-11, said substrate boardcomprising a resin selected from the resin group consisting of vinylchloride, acrylic, polycarbonate, polyethylene phthalate and olefinresins.
 13. A decorative board of any of claims 8-12, each of saiddecorative sheets comprising a resin impregnated and hardened sheet. 14.A decorative board of any of claims 8-13, wherein said substrate boardis a glass pane.
 15. A decorative board of any of claims 8-14, whereinsaid substrate board comprises a prepreg comprising layeredthermosetting resin sheets or thermosetting resin impregnated andhardened paper sheets.
 16. A decorative board comprising a translucentsubstrate board and a translucent decorative panel, said substrate boardand said decorative panel being integrated with each other.
 17. Adecorative board of claim 16, wherein said decorative panel comprises aplurality of partially overlapping print layers of different colorsformed on a paper sheet, which are impregnated with a thermosettingresin, said print layers comprising numerous color dots.
 18. Adecorative board of claim 16, wherein said decorative panel comprises aJapan paper or vashi sheet impregnated with a thermosetting resinsandwiched between resin impregnated paper sheets, which are bondedtogether and hardened by thermo-compression.
 19. A decorative board ofclaim 16, wherein said decorative panel comprises a substrate papersheet having at least one printed portion and at least one non-printportion in a pattern, which is impregnated with a resin, said non-printportion having an optical transmittance greater than said printedportion.
 20. A decorative board of claim 16, wherein said decorativepanel comprises a substrate paper sheet impregnated with a thermosettingresin.
 21. A decorative board of claim 16, wherein said decorative panelcomprises a printed paper sheet impregnated with a thermosetting resin.